Nadal leads banged-up players who need to bounce back in 2013

Rafael Nadal hasn't played since Wimbledon as he recovers from a lingering knee issue. (Zumapress)

Bad knees. Twisted ankles. Irregular tickers. A lot of talent was left on the bench in 2012 because of unforeseen injury and illness, knocking out some key contenders and derailing -- or at least putting on pause -- the careers of a few promising young stars. Here are five players we missed in 2012 and hope to see more of in the new season.

Rafael Nadal (Current ATP ranking: 4): He hasn't played a match since June because of a knee injury, but Nadal finally made it back onto the practice courts a month ago. We'll get our first look at Rafa next week when he takes the court Dec. 28 for the Mubadala World Tennis Championship in Abu Dhabi, where he'll take on the winner of Andy Murray vs. Janko Tipsarevic. If it turns out to be Murray, well, what a way to start the season. (UPDATE: Nadal withdrew from the exhibition with a stomach virus.)

Nadal's camp is already downplaying his chances in Australia, which is understandable. And Nadal himself has expressed his doubts about the status of his knee. By the time the Australian Open rolls around in mid-January, Nadal will have spent only two months hitting on the court after a five-month layoff. The early hard-court season will be about playing himself into match fitness, building confidence and learning to trust his body again. The real test will come when his sneakers hit the red clay in April. Even when he's at his best there are explanations as to why Nadal is susceptible to losses on hard and grass. But he's the King of Clay for a reason, and if he can't dominate the dirt this year the way he has in the past, the disappointment and doubt could undo his year.

Andrea Petkovic (Current WTA ranking: 125): Do not adjust your dials. Everyone's favorite dancing German is indeed down to a lowly No. 125 after starting the season as a top-10 player only to suffer a back injury that forced her out of the Australian Open. She returned three months later and won her first match back, in Stuttgart, but sustained a horrible ankle injury in her next match. You could see her reaction to this string of bad luck all over her face as she lay on the court awaiting medical attention: You've got to be kidding me. Not again.

This wasn't the first year Petkovic's body failed her. She suffered an ACL tear after two minutes of play in her first-round match at the Australian Open in 2008, which kept her off the tour for eight months. So she's fought back from injury before. The question is whether, at 25, Petkovic has one more comeback in her. It took a tremendous effort for her to break into the top 10 and a year later she's basically starting from scratch. In fact, if she isn't granted a wild card, she'll have to play the qualifying tournament to get into the main draw of the Australian Open. Success in the first half of the season will stoke the fire for a full-fledged comeback. But if she doesn't get the results, I'd worry about Petkovic's motivation level. She's a hard worker, but she's also a realist.

Mardy Fish(Current ATP ranking: 27): It was a worrisome and scary year for Fish, who had to be rushed to the hospital in the spring after suffering what, at the time, seemed like a panic attack. In fact, doctors discovered that Fish had an irregular heartbeat, and he underwent a medical procedure to fix it. Just when it seemed like Fish was well on his way to recovery and finding consistent success on the court, the concerns returned at the U.S. Open, where he gave Roger Federer a walkover into the quarterfinals after complications related to his heart forced him to withdraw. At 31, Fish is still capable of playing top-10 tennis, and it would be great to see him bounce back in 2013 and put this difficult year behind him. But if the health concerns still plague him next season, then it's likely we've seen the best of Fish.

Gael Monfils (Current ATP ranking: 77): Tennis lost a lot of pure athleticism with Monfils' knee injuries sidelining him for much of the 2012 season. He's the most exciting player to watch, but recklessly throwing his body around the court finally caught up to him. The question is whether Monfils has learned his lesson and will come out playing more offensive tennis to keep points and matches short. I wouldn't put too much hope in a change of tactics. The joy we get from watching Monfils play rarely has anything to do with his win-loss record or efficiency. We watch -- and I suspect he plays -- for the chance to make that skidding, leaping, airborne play that no one else on tour has the guts to play. Viva Le Monf!
Svetlana Kuznetsova(Current WTA ranking: 71): I can never make up my mind on whether the two-time Slam champion has overachieved or underachieved in her career. She is the WTA equivalent of Marat Safin in that way. Her athleticism and raw talent should make her a contender every week, but that brain of hers seems to always get in the way. You never know what you're going to get from the Russian on any given day, and her own lack of clarity doesn't help either. Kuznetsova didn't pick up a racket for the rest of the year after losing in the first round at Wimbledon, opting to heal and treat a knee injury. She's back on the courts practicing, though, and we'll just have to wait and see how her form goes through the season. When I spoke with her at Indian Wells last spring, she already seemed weary, confused and over all her on-court struggles. It's entirely possible that the injury break did her mental state good.

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